One of the conventional manners of attaching wheel covers made of plastics to the disc wheel rims of the vehicle comprises attaching a wire ring from inside to circular stopper ribs arranged integral along the circumferential rim of the wheel cover on the backside thereof to resiliently urge the circular stopper ribs outward. An example of this approach is disclosed in U.S. Pat. No. 4,027,919 another approach disclosed, e.g., in U.S. Pat. No. 2,746,805, involves inwardly curving a part of such a wire ring to produce a spring force. A further approach proposed by the applicant of the present invention as a Japanese Utility Model Application Sho No. 60-66209 comprises arranging a plurality of outer and inner stopper ribs along the circumferential rim of the wheel cover on the backside thereof and inserting a plate spring between the outer and inner stopper ribs, respectively, wherein the spring pressure of each of the plate springs is adjusted to hold the wheel cover onto the wheel rim.
However, engagement between the wheel covers and rims becomes inferior relatively soon because of deterioration of the plastics of which the stopper ribs on the backside of the wheel covers are made. In addition, the spring pressure of the wire ring and those of the plate springs are likely to become deteriorated. Further, it is difficult to adjust them to have an appropriate spring pressure. Therefore, any successful and satisfactory arrangement has not been proposed yet to attach the wheel covers made of plastics to the wheel rims.